Electrical motor drive system with field control operable in motoring and braking modes

Claim 2

A drive system wherein d-c electric motor means comprising armature and field means are coupled to a mechanical load to drive the load in a motor mode and to be driven by the load in a braking mode so as to generate armature current dissipated in a braking load circuit and retard motion of the load, comprising: a. a source of d-c energy having first and second conductors; b. armature means and field means; c. motor-brake switching means coupled in circuit between said armature and field means to connect said field and armature means in a series circuit with said source only during the motor mode; d. power conversion means having its output coupled to shunt said field means and operable in inversion or rectification modes to selectively shunt armature current from said field means during the motoring mode to provide field weakening, and to provide excitation current to said field means during the braking mode.

Claim 3

The arrangement of claim 1 wherein said armature means is coupled to said first conductor, said field means is coupled to said second conductor, and means for establishing a braking energy absorption circuit with said armature means during the braking mode.

Claim 4

The arrangement of claim 2 wherein said armature means is coupled through variable impedance means to said first conductor for controlling armature current.

Claim 5

The arrangement of claim 3 wherein said variable impedance means comprises periodically actuated chopper means whose conduction duty cycle is variable to control armature current.

Claim 6

The arrangement of claim 4 comprising first control means operative during the motor mode for increasing the conduction duty cycle of said chopping means with increasing speed of said d-c electrical motor means and second control means operative during the motor mode to shunt armature current from said field means upons said chopper means attaining a predetermined conduction duty cycle.

Claim 7

The arrangement of claim 5 wherein the magnitude of the armature current shunted from said field means is controlled to maintain armature current at a predetermined relationship to the speed of the motor means.

Claim 8

The arrangement of claim 6 wherein said first control means maintains said armature current constant during a predetermined speed interval.

Claim 9

The arrangement of claim 7 wherein the first control means modifies the conduction duty cycle of said chopper means to maintain a constant armature current over a first predetermined motor speed interval and said second control means modifies the magnitude of armature current shunted from said field means over a second predetermined motor speed interval to control armature current until field current is reduced to a predetermined portion of armature current.

Claim 10

The arrangement of claim 2 wherein said power conversion means comPrises d-c to a-c to d-c conversion means having a d-c input coupled to said source of d-c energy and a d-c output variable intermediate predetermined valuse of rectification and inversion.

Claim 11

The arrangement of claim 9 wherein said conversion means comprises d-c to a-c inversion means and phase controlled rectifying means, said phase controlled rectifying means having an a-c input supplied from said d-c to a-c inversion means and a controlled output coupled across said field means.

Claim 12

The arrangement of claim 10 wherein said phase controlled rectifying means comprises controlled rectifier means, and control means for controllably phasing the firing said rectifying means in respect to said a-c input to provide for selective variation of said output between predetermined voltage magnitudes of one polarity (i.e., inversion) and of an opposite polarity (i.e., rectification);

Claim 13

The arrangement of claim 11 wherein said control means is adapted to selectively advance firing of said rectifying means during the motoring mode to shunt armature current through said controlled rectifying means and to further advance firing of said rectifying means during the braking mode to provide evergization current to said field means.

Claim 14

An electric drive motor system wherein d-c electrical motor means are energized from an electrical source in a motoring mode and wherein during a braking mode said motor means operates as electrical generating means providing electrical energy to a braking load comprising: a. a source of d-c energy comprising first and second conductors; b. motor armature chopper means; motor armature means, motor switching means, and motor field means connected in the order recited in a series circuit between said first and second conductors; c. rectifying means connected in parallel with the serially connected combination of said armature means motor switching means and motor field means, and poled to pass motor armature current during intervals when said chopper means is cut off; d. means adapted to couple a braking energy absorption circuit with said armature means to pass armature current during turn off of said chopper means in the braking mode; e. power conversion means producing a controllable d-c output, variable between a maximum value of one polarity to a maximum value of the opposite polarity, said output being coupled across said motor field means; f. control means for controlling the output of said power conversion means to selectively energize said field means during the braking mode and to shunt selective portions of armature current about said field means during the motoring mode, and g. means for closing said motor switching means during the motor mode, but not during the brake mode to serially connect the chopper means, armature means and field means across said source.

Claim 15

An electric drive motor system wherein d-c electrical motor means are energized from an electrical source in a motoring mode and wherein during a braking mode said motor means operates as electrical generating means providing electrical energy to a braking load comprising: a. a source of d-c energy comprising first and second conductors; b. motor armature chopper means; motor armature means, motor switching means, and motor field means connected in the order recited in a series circuit between said first and second conductors; c. rectifying means connected in parallel with the serially connected combination of said armature means motor switching means and motor field means, and poled to pass motor armature current during intervals when said chopper means is cut off; d. means adapted to couple a braking energy absorption circuit with said armature means to pass armature current during turn off of said chopper means in the braking mode; e. power conversion means producing a controllable d-c output, variable between a maximum value of one polarity to a maximum value of the opposite polarity, said output being coupled across said motor field means; f. control means for controlling the output of said power conversion means to selectively energize said field means during the braking mode and to shunt selective portions of armature current about said field means during the motoring mode, and g. means for closing said motor switching means during the motor mode, but not during the brake mode to serially connect the chopper means, armature means and field means across said source.

Claim 16

The arrangement of claim 13 adapted for regenerative braking wherein said rectifying means is coupled from one terminal of said motor armature means to said first conductor and means adapted to pass current solely during the braking mode coupled from the other terminal of said motor armature means to said second conductor.

Claim 17

The arrangement of claim 14 wherein said means adapted to pass current comprises unilaterally conducting means poled to pass armature current generated during the braking mode.

Claim 18

The arrangement of claim 13 wherein said power conversion means comprises d-c to a-c to d-c inversion means having its d-c input coupled to said source of d-c energy.

Claim 19

The arrangement of claim 16 wherein said d-c to a-c to d-c inversion means comprises first inverting means for inverting d-c energy to a-c energy, and second means comprising phase controlled rectifying means for converting a-c energy to d-c energy appearing at the output of said conversion means, said control means comprising means for selectively advancing the firing of said rectifying means during acceleration in the motoring mode and for selectively further Advancing the firing of said rectifying means deceleration in during the braking mode.

Claim 20

The arrangement of claim 17 wherein said second means comprises a center-tapped transformer winding and first and second semiconductor controlled rectifiers connected in a full wave rectifying arrangement about said motor field means, and the a-c output of said first inverting means is transformer coupled to center-tapped winding.

Claim 21

The arrangement of claim 18 wherein said first inverting means comprises static d-c to a-c converting means commutated at a predetermined frequency.

Claim 22

The arrangement of claim 16 comprising plural d-c electric motor means connected in parallel to one another; and wherein said d-c to a-c to d-c inversion means comprises a common inverting means for inverting d-c energy to a-c energy, and plural a-c to d-c conversion means, the output of each of said a-c to d-c conversion means being coupled in shunt with the field means of a different one of said parallel connected motor means.

Claim 23

The arrangement of claim 20 wherein each of said a-c to d-c conversion means comprises phase controlled rectifying means, said control means comprising means for selectively advancing the firing of said rectifying means during the motoring mode and for selectively further advancing the firing of said rectifying means during the braking mode.